In Spanish-speaking countries, Diego and Santiago are common as given names; Diego, Santiago and Sandiego are found as surnames.
The forms Tiago, Thiago, Diago and Diogo are seen mostly in Portuguese speaking countries. The name Diego can also be found in Italy.[citation needed]

Contents

During the medieval era, the names "Sant Yago", "Diago" and "Diego" coexisted. "Sant Yago" is used, for example, in a letter by James II of Aragon dated 1300: "[...] maestro de la cavalleria de Sant Yago et de la dita orden [...]".[1]

The patronymic for Diego is Díaz in Castillian (used for example by Rodrigo Díaz de Vivar, better known as El Cid) and Diasin Portuguese. Like many patronymics, these have become common surnames in Spanish- and Portuguese-speaking regions. The form Diéguez is much less common; Diegues can be found in Portuguese-speaking countries. de Diego and Diego can also be found as surnames.